Septic Systems
How Do They Work?
The Basics
Types of Septic Systems
How to Choose the
Right Septic System
One-size-fits-all, does not apply to septic systems. Multiple factors determine the type(s) of septic systems that can be installed on a residential or commercial property, including:
- Household size
- Lot size
- Soil type
- Site slope
- Proximity to well or water sources
- Even weather conditions
- Local & state regulations
On-Site Sewage Facilities (OSSF), commonly called a “septic system” must be designed on a per property basis. This requires an an onsite inspection by a OSSF licensed site evaluator.
At the site inspection, your site evaluator can determine the type(s) of septic system(s) that can be installed on the property according to regulations by the local municipalities and/or state.
According to the Texas Commission on Environmental Quality (TCEQ), “Site evaluations determine local conditions and the design of OSSFs. In many parts of Texas, soil analyses are ruling out conventional systems where liquids are separated from solids in the septic tank and then spread throughout the drainfield by means of underground pipes or other proprietary products. Organic wastes are treated as the liquids percolate through the soil. But most soils in Texas can’t properly absorb pollutants, so alternative treatment methods are required.”
SepticSmart Tips
Septic System Basics
How Do Septic Systems Work?
Septic Tanks
Constructed to be watertight, the septic tank is buried and connected to all of the drainage pipes. The tank catches all of the raw effluent (wastewater) that flows down the drains. The heavy solids settle at the bottom of the tank, while the lighter solids float to the top. As the wastewater flows through the tank and gets discharged into the drainfield, the gravel and stone act as a filter, continuing to breakdown the wastewater before it is dispersed into the surrounding soil.
Types of Septic Systems
Conventional Septic System
This is an anaerobic system typically installed at a single-family home or a small business. A conventional septic system features a gravel/stone drainfield, a design that has been used for decades.
This system that features a decentralized wastewater treatment system that consists of a septic tank and a trench, and a drainfield (bed subsurface wastewater infiltration system).
The waste is piped from the septic tank to a shallow underground trench lined with stone or gravel. A geofabric material (permeable tough synthetic geotextile) is then placed on top of the trench to prevent sand, dirt and other contaminants from accessing the clean gravel.
The wastewater is filtered through the gravel, and then further treated by microbes once it reaches the soil below the gravel trench. Due to the size of the drainfield, this system may not be suitable for all sites.
Chamber Septic System
This is an alternative design to the gravel/stone system. The chamber septic system is an anaerobic system that can be manufactured with recycled materials. There are several advantages to the chamber system, including:
- Reduces the carbon footprint
- Easy to set up and construct
- Works in areas where gravel is scarce
- Suited for areas with high groundwater tables
The system features a series of connected chambers that are filled with soil. The area around the system is also covered with soil. The wastewater released from the tank flows through the chambers and the microbes in the soil treat the wastewater.
Mounds System
This system is ideal for areas that have shallow soil, high groundwater, or shallow bedrock.
This system does not have a large buried drainfield. The wastewater goes into the septic tank and then flows by gravity to the pump chamber where the solid waste is separated and filtered. Low pressure controlled portions of liquid are then released through perforated pipes so it can be distributed into the mound of sand uniformly. The liquid trickles down through the sand and gravel for further filtration before reaching the native soil.
Although this can be a great solution for certain areas, it does require more space, and regular maintenance.
Drip Distribution System
The drip distribution system can be used with many types of drainfields. The main advantage of the drip distribution system is that no large mound of soil is needed as the drip laterals are inserted into the top 6 to 12 inches of soil. The disadvantage of the drip distribution system is that it requires a second tank to hold the liquid that flows out of the septic tank to accommodate the controlled portion of of the wastewater that will be released in the drip absorption area. This system also requires electrical power, an added expense, as well as increased maintenance.
Anaerobic vs. Aerobic Septic Systems
Aerobic Treatment System
This system is 30x more efficient than an anaerobic system. Aerobic systems use bacteria that require oxygen to survive. Oxygen is pumped into the tank to activate the bacteria, which then feeds on the solid waste. Aerobic systems work well where the soil isn’t favorable for other systems and the groundwater table is high. It’s a good option for homes located near a body of water. This system requires additional components to operate: an air pump and electrical power.
According to According to the Texas Commission on Environmental Quality, “Aerobic systems are more complex and require more maintenance. Some maintenance may be performed by homeowners for systems using secondary treatment or drip irrigation, and surface application disposal.
Some permitting authorities have adopted more stringent requirements, which may require homeowner training or even prohibit homeowner maintenance. Check with your permitting authority to find out if it has adopted more stringent requirements.“
Anaerobic Septic System
Anaerobic systems are a common choice for many homeowners because they do not require electrical power or chemicals. An anaerobic system contains bacteria that does not need oxygen to survive. The bacteria breaks down solid waste, and the remaining liquid waste is piped out and distributed under the soil. The waste is naturally recycled as the water passes into the soil.
Anaerobic septic systems:
- Conventional Septic System
- Chamber Septic System
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